1. Field of the Invention
The present invention relates generally to balancing machines, and more particularly to a machine for determining the mass center of a rotating body and for marking the axis of inertia of the body.
2. Description of the Related Art
If the net mass distributed within a rotating body is asymmetrical to the body's axis of rotation, vibrations will be imparted to the body's bearings due to the centrifugal forces generated by the asymmetrical mass. If an axis of rotation can be found for the body such that the axis passes through the center of the body's mass, the net distribution of mass will be symmetrical about that axis and vibration will not be imparted to the body's bearings. Such an axis that passes through the body's center of mass is known as the body's axis of inertia. Physical laws establish a relationship between the location of a body's axis of inertia and the centrifugal forces generated when the body is rotated about an axis other than its axis of inertia. A mass centering machine determines and marks the axis of inertia in a body by measuring the unbalance in a body, calculating the distance between the body's axis of inertia and the centerline about which it was rotated as unbalance measurements were taken, and aligning the body's axis of inertia with the centerline of a marking device which makes a mark on the body indicative of a point through which the axis of inertia passes.
In order to align an article's axis of inertia with the centerline of a marking device, prior art mass centering machines shift either the article, the marking device, or both, in a combination of a minimum of two movements, as least one of which is linear. This linear movement may shift either the article or the marking device, the maximum amount of shifting required usually being very small. In order to obtain acceptable accuracy, this small shift must be divided into as many steps as possible, requiring expensive adjusting devices. As the stroke of the slide providing linear movement is very short, wear is confined to a small area of the slide. In some cases, especially in cases of two plane balancing, the devices providing X and Y adjustments are rotated with the article, resulting in structurally complicated and expensive mechanisms.